High-Efficiency Solenoid Coil Structure for Induction Heating of Cylindrical Heating Object

The solenoid coil is a typical heating coil structure for induction heating of cylindrical heating objects. Conventionally, a bare solenoid coil without any soft-magnetic core has been commonly utilized. However, this conventional structure suffers from worse heating efficiency caused by the large coil copper loss and the low magnetic field induction at the heating object. This paper addresses these difficulties by proposing a novel heating coil structure. In addition to the solenoid coil, the proposed heating coils structure further incorporates the soft-magnetic cores that cover the outer coil periphery and the coil opening edges. These additional cores can reduce the local intense magnetic field around the coil, thus mitigating the eddy current induction inside the wire to reduce the copper loss, and also can increase the magnetic field inside the heating object, thus increasing the heat generation. The simulation was carried out to test the effectiveness of the proposed heating coil structure. The results inferred the reduction of the coil copper loss by 25% and the increase in the heat generation in the heating object by 53%, both of which suggest the promising features of the proposed heating coil structure for heating the cylindrical magnetic material. The heating operation of the proposed heating coil structure was tested by the experiment, although the current prototype was found to have larger power loss than expected from the simulation. The reason may lie in unintended eddy current generation of the metal case of the heating coil, which will be addressed in future work.